Iran announced this week that authorities broke up "the biggest terrorist plot“ targeting the capital Tehran and other areas of the country. Iran's Intelligence Ministry said a “Takfiri” terrorist group had planned a series of bombings over the coming days.

Here is what the term "Takfiri" means and how extremist groups and the Iranian regime use it against their rivals.

What is Takfirism?

Takfir is an Arabic word used to describe a Muslim as infidel or non-believer. The practice of accusing another Muslim of apostasy or declaring another Muslim as infidel is called Takfir.

According to Pakistani religious scholar Javed Ahmad Ghamidi, “A Muslim or a Muslim group is Takfiri if it declares another Muslim or a Muslim sect as apostate.”

How is the term Takfiri used in the Muslim World?

The term Takfiri is used by some extremist groups that see Islam through a narrow keyhole of self-righteousness and consider other Muslims or certain groups of Muslims as apostate. They use the term against those who may not agree with their ideology or refrain from pledging allegiance to them. Takfiris prescribe the death penalty to the apostates.

A number of Sunni extremist outfits in Pakistan, including the Lashkar-i-Jhangvi group, have used the term to describe Muslim Shi’ites as being out of Islam or apostate. Similarly, certain Shi’ite groups such the Tehrik-e-Jafaria Pakistan have used the term for Sunnis or certain Sunni groups in the country.

Mainstream Sunni and Shi’ite leaders often refer to armed extremist groups as Takfiris.

The number of Takfiri groups in the Muslim world, however, is very small.

Who are Takfiris?

Pakistan-based Fulbright scholar in religious studies, Qibla Ayaz, traces Takfiris’ history to the creation of the Khawarij group in the very first century of Islam.

According to Ayaz, the Khawarij, who were outcasts from mainstream Muslims, broke into revolt against Caliph Ali. A cousin and son-in-law of Prophet Muhammad, Ali was the fourth caliph of Islam. The Khawarij later assassinated him, as he did not agree with their war demands against another group of Muslims.

Are there Takfiri Groups in Shi’ite Islam?

There have been a number of Shi’ite groups that labelled their rivals as infidels. “If declaring other Muslims apostates is Takfirism, then religious literature in Shi’ite Islam provides materials that call its ideological opponents as apostates,” Ghamidi told VOA. He added that the followers of the top Shi’ite Takfiri leader, Hasan bin Sabbah, used tactics including suicide attacks against their rivals.

Who has the authority to declare others as apostates?

Despite the fact that Islam does not grant religious groups the authority to label other Muslim groups as infidels, certain Muslim religious bodies in Pakistan have done so. Ghamidi believes that only states should have such an authority to declare which Muslim groups are outcast from the mainstream Muslims. Most Muslim states have official religious bodies “Darul Ifta” that are responsible for issuing final decrees pertaining to major religious issues that may arise in the country. Decrees are made based on deep knowledge of Islam and taking socio-economic and scientific evidence and logical, historic and comparative perspectives, and contemporary conditions surrounding an issue into consideration.

How is Iran using Takfirism against regional rivals?

The current regime in Iran has widely used the Takfiri term for militant groups that may have links with regional Sunni states such as Saudi Arabia or groups that may challenge the might of the regime.

Tehran uses the Takfiri term not only for Islamic State in Syria, but it also describes all militant groups that are fighting the Syrian regime as “Takfiris supported by Western countries.”

Is Islamic State a Takfiri Group?

Both Ayaz and Ghamidi believe the Islamic State group fits in the definition of Takfir in modern Muslim history.

“[Islamic State] considers its rival Sunni Muslim groups, all the Shi’ite Muslims and its ideological opponents, apostates,” Ayaz said. “The followers of [IS] also believe in taking properties of their enemies as war booty and take their enemies’ women as concubines, a practice approved per Takfiri ideology.”